I love tower defense games that also bring in some other gameplay type, and X-Morph: Defense does this incredibly well. It’s as much a twin-stick shooter as it is a tower defense game. Similar to Sanctum (another favorite of mine), each wave starts with maze-like tower placement, but once the enemies enter, it becomes an action-packed shoot ’em up. That doesn’t mean rearranging towers is then off limits, though. In particularly difficult levels, it became necessary to build, upgrade, and move towers on the fly as the enemy clusters grew/shrank. It’s nice that moving/selling towers doesn’t incur a penalty, giving you plenty of freedom to experiment and re-plan your strategy when things don’t go your way.
And, oh, how things don’t go your way. X-Morph: Defense can be very difficult. The difficulty is pretty up and down, though. Some levels start out feeling impossible, but once you earn more money and can place more towers, they become too easy. Other levels start out easy and then beat you to a pulp in the final wave. I found myself constantly needing to scrap my entire layout and reorganize everything. But, again, I appreciated that I was allowed and encouraged to do so. The enemy patterns frequently change, anyway, so you can never truly be married to your original ideas. Plus, the entire campaign is co-op compatible, meaning you and a friend can fuss over the perfect tower placement together, just like friends are meant to do.